Even through orthodontists have traditionally focused on anteroposterior dentoskeletal relationships, many malocclusions are due to abnormal vertical development. A thorough understanding of both normal and abnormal vertical growth is necessary to evaluate developing malocclusions and more effectively treat patients with hyperdivergent and hypodivergent phenotypes.

Although various measurements have been used to classify vertical malocclusions, their validity remains to be established. Classifications have been based on dental overbite, the upper-to-lower anterior facial height ratio, the posterior-to-anterior facial height ratio, the mandibular plane angle, the palatal plane angle, the palatal-to-mandibular plane angle, the gonial angle, and even the perception of increased or reduced lower facial height. In the only study in which the authors statistically evaluated whether typically used measurements reflect the same aspects of vertical discrepancy, Dung and Smith showed a high correlation (0.90) only between the mandibular plane angle and the posterior-to-anterior facial height ratio; of the remaining 20 correlations, 4 were moderately low, and the rest were low or very low. If the various measurements are more or less independent of each other, they represent different phenotypic attributes and cannot be used interchangeably for vertical classification of patients.

Reference data for longitudinal vertical growth of adolescents are inconsistent and limited. The palatal plane angle has been reported to increase between 10 and 15 years of age for girls and decrease for boys. With the sexes combined, the palatal plane angle has been shown to both increase and decrease. The upper-to-lower facial height and the posterior-to-anterior facial height ratios have also been reported to both increase and decrease during adolescence, depending on the sample and the sex. Although most studies have shown that the mandibular plane angle decreases during adolescence, Bhatia and Leighton showed slight increases between 10 and 15 years. The palatal-to-mandibular plane angle is the only measurement showing consistent changes (increases) across studies. Importantly, longitudinal reference data for adolescent vertical development are based on relatively small samples (usually <75 subjects), making it difficult to estimate the extreme percentiles, where many orthodontic patients might be expected to be located.

To determine the appropriate timing of treatment, it is also important to determine whether the growth patterns of untreated hyperdivergent or hypodivergent patients remain stable. Based on a sample of 20 male and 15 female subjects, Bishara and Jakobsen showed that 77% maintained their facial type between 5 and 25.5 years of age; the rest normalized, or became more hyperdivergent or more hypodivergent. Based on a larger sample, it has also been shown that 33% to 64% of those classified as having either high, average, or low mandibular plane angles at 6 years of age maintained their classification through age 15. Their mandibular plane angles either improved or worsened over time, but the differences averaged out because the growth curves representing the subsamples with high, average, or low angles maintained the group differences between 6 and 15 years.

Larger sample sizes and more reliable estimates of vertical growth are necessary to reconcile the inconsistencies. This project’s overall aim was to describe the vertical growth changes that occur during adolescence. The specific aims were to provide reference data for the vertical growth changes that occur; evaluate the associations between measurements used to describe vertical development; determine whether subjects classified as hypodivergent, within normal limits, or hyperdivergent maintain their classifications between 10 and 15 years of age; and compare growth changes of subjects classified as hypodivergent, within normal limits, or hyperdivergent.